Upgrade from 2.2 to 2.3

I have a client wanting to upgrade from 2.2 to 2.3 (2.3.3)

They have several MODX sites including 2.3 versions and are wanting 2.3 on an older 2.2.6 modx install.

Is there any reason to be worried about doing a 2.2 to 2.3 upgrade? Are there any incompatibility issues? Can I just follow standard upgrade procedures? Is it impossible? Thanks for any insight.

I don't know if this list is still current, but I'd definitely check your extras against it to see if you're running anything that might break on 2.3
https://github.com/modxcms/revolution/issues/11630

I've updated many sites from various incarnations of 2.2 to 2.3 and every problem I experienced was tied to one of two issues: 1) extra incompatibility, 2) uncleared cache and session data (both client and server side). If you're extras show as compatible and you're careful to clear your cache, user sessions, and local browser cache, you should be able to make the upgrade pretty uneventfully.